Torsional vibration damper

Abstract

A torsional vibration damper having enhanced vibration damping performance is provided. The torsional vibration damper comprises: a vacant area existing between an outer circumference of the sun gear and an inner circumference of the ring gear outside of a revolving range of the planetary gears revolved as a result of relative rotation between the sun and the ring gear; and a mass increasing portion that is formed on the rotary member other than an input element and an output element within the vacant area in such a manner as to protrude from the rotary member.

What is claimed is: 
     
       1. A torsional vibration damper, having:
 a planetary unit that performs a differential action among a sun gear, a ring gear arranged concentrically with the sun gear, and a carrier supporting pinion gear interposed between the sun gear and the ring gear in a rotatable and revolvable manner; 
 wherein any of the sun gear, the ring gear and the carrier serves as an input element to which torque is applied, and any of another rotary element serves as an output element; and 
 wherein the input element is connected to the output element through an elastic member while being allowed to rotate relatively with each other; 
 the torsional vibration damping device comprising: 
 a vacant area that exists between an outer circumference of the sun gear and an inner circumference of the ring gear outside of a revolving range of the pinion gears revolved as a result of relative rotation between the sun gear and the ring gear, wherein the vacant area is an unused area of the sun gear, in which the pinion gears do not roll; and 
 a mass increasing portion that is formed on the ring gear other than the input element and the output element within the vacant area in such a manner as to radially protrude from the ring gear. 
 
     
     
       2. The torsional vibration damper as claimed in  claim 1 ,
 wherein the mass increasing portion is formed on the sun gear.